Breast nipple aspirate fluids (NAF) are useful for non-invasive monitoring of the breast. NAF has been shown to exhibit large inter-individual differences in lipid peroxidation. Unfortunately, the yield of epithelial cells in NAF is low. More recently, breast ductal lavage has been approved for clinical use. Nuclear morphologic features of breast biopsies have been shown previously to have prognostic value for breast cancer risk. In women without cancer, there may be subtle changes in the breast epithelial cells that can only be defined with computer-assisted measurements. The subjects selected for this study will be 98 women with biopsy-confirmed proliferative breast disease. These women are at slightly increased breast cancer risk, and exhibit higher mean levels of cholesterol and cholesterol oxides in NAF than women with non-proliferative histology in the breast. Levels of 8-isoprostane, cholesterol, fatty acids, fat-soluble micronutrients and 2,6-cyclolycopene-4,5-diol will be quantified in breast NAF that is obtained before breast lavage. These measures were chosen based on their potential relationship to dietary intakes and to oxidative stress, which is relevant to the application of these methods to dietary prevention studies. We will characterize the morphology of breast epithelial cells from lavage using quantitative image cytometry to capture nuclear and cellular area, diameter, roundness, perimeter, and nuclear:cytoplasmic area ratio. Correlations will be evaluated between the measured morphologic features and each analyte in the NAF. The impact of various clinical, demographic and dietary factors on cellular morphology will also be explored. This study will help establish the feasibility of using these measures as endpoints in dietary intervention studies and will generate hypotheses that should be tested in larger studies. Such measures also should be applicable to molecular epidemiological investigations that seek to examine the impact of certain gene polymorphisms and environmental exposures on biomarkers of cancer risk.